docs: Send Data Alloy page + Interactive Examples

This PR updates the send-data section of the documentation with an Alloy introduction and examples directory. Each of the examples are written as interactive sandboxes using the documentation found here: https://github.com/grafana/killercoda/blob/staging/docs/transformer.md

Note this PR also includes a new writers shortcut

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Here are the Interactive sandboxes auto-generated from the docs:

Checklist

[x] Reviewed the CONTRIBUTING.md guide (required)
[x] Documentation added
[x] Documentation contains interactive example
[ ] Tests updated
[x] Title matches the required conventional commits format, see here
- Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
[ ] Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
[ ] For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
[ ] If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

grafana / loki